Evaluation of safety and efficacy of microbicides requires an assessment of potential injury caused by micobicides in the epithelium of cervicovaginal tract and rectum. The development of imaging technology and protocols that can be used for endoscopic, rapid, and quantitative assessment of tissue injury following topical application of microbicides could have significant impact on the development and testing of microbicides in animal models and clinical studies. Unfortunately, current imaging technology such as white light colposcopy or colonoscopy cannot provide high resolution images of epithelial injury and cannot probe below the surface where epithelial injury and inflammation may be evident. However, in recent years, new imaging technology has been developed where it is now possible to perform high resolution imaging of epithelial tissue with microscopic resolution in vivo. Our overall goal is to develop an endoscopic imagedbased approach that can be used to 1) assess the degree of injury that may be induced by microbicides and 2) correlate the results of imaging studies to susceptibility to genital infection in mice cervicovaginal tract and rectum caused by HSV-2. We will deploy emerging high resolution imaging modalities including confocal fluorescence microscopy and optical coherence tomography (OCT) to characterize the changes that occur in the architecture of cervical, vaginal, and rectal epithelium of untreated sexually na[unreadable]ve mice as well as mice treated with known irritative microbicides. These results will be correlated to susceptibility to infection using a well characterized mouse model of HSV-2 infection. This will allow us to assess the predictive value of confocal fluorescence and OCT imaging for observed HSV-2 susceptibility based on microbicide-induced epithelial changes with attention to reproducibility/consistency of findings. In phase I of this project we will demonstrate the capabilities of high resolution optical imaging to quantitatively assess the response of cervicovaginal and rectal tissue to known microbicides and test the ability to predict the biological end point of microbicide-induced changes in susceptibility in cervicovaginal tract. In phase II, the proposed imagedbased assessment of rectal response will be extended to establish correlation between image-based markers and rectal susceptibility following application of microbicides. Furthermore, instrumentation and imaging parameters will be optimized to make the imaging protocol suitable for imaging of cervicovaginal and rectal epithelial response in large animal models and humans. We also plan to use the developed imaging protocol to assess the performance of novel microbicides in small animal models as new products are developed.